Characteristics of mass lesion presentation of primary angiitis of the central nervous system: A single center 11-year retrospective case-series study

Objective: Mass lesion presentation of primary angiitis of the central nervous system (ML-PACNS) is a special subtype of primary central nervous system vasculitis, which is difficult to be differentiated from other space occupying disorders. We aimed to summarize our experience and improve diagnostic techniques of ML-PACNS. Patients and methods: Case records for 16 patients treated in the Department of Neurology of Six Medical Center of Chinese PLA General Hospital from December 2008 to November 2019 were examined. All patients were diagnosed with ML-PACNS by pathology. Clinical manifestations, neuroimaging results and pathological features were retrospectively analyzed. Results: The 16 patients with ML-PACNS in the cohort (8 males) had a median age of 32 (range 19-56 years). On T1WI and T2WI, 12 cases showed mixed signals and 4 cases showed T1WI hypointense and T2WI hyperintense. Fifteen patients showed DWI hyperintense, of which 9 cases showed hypointense in the middle of the lesion. Gadolinium enhancement of all cases was irregular. All patients had a brain biopsy (stereotactic procedure in 10 and open-wedge surgery in 6) which showed lymphocytic vasculitis in the majority of patients (15/16) and necrotizing vasculitis in one patient. Conclusions: ML-PACNS is an important differential candidate for tumefactive demyelinating lesions, CNS infections and brain tumors. Mixed T1WI and T2WI signals as well as central hypointense surrounded by hyperintense lesions on DWI may be useful imaging features for the diagnosis of ML-PACNS which has implications for those who have not yet had a biopsy. ML-PACNS may have different pathological type from PACNS.